The overall objectives of this project are twofold: first to examine the mechanisms responsible for alterations in cerebral microvascular hexose transport and fuel metabolism we have observed in the diabetic rat; and second to examine the relationship between these alterations and the regulation of myo- inositol transport, NaKATPase activity and polyol metabolism. The proposed studies will utilize intact rats, isolated microvessels and glomeruli and cultured microvascular cells. The specific aims are as follows: 1). To determine the factors and mechanisms responsible for the downregulation of hexose transport across the blood-brain barrier (BBB) of diabetic rats. Hexose transport in vivo will be related to alterations in hexose transporter number, structure and (mRNA) in microvessels isolated from diabetic and other rats in which plasma insulin or glucose are chronically altered. 2). To examine the mechanism(s) by which hyperglycemia downregulates hexose (3-methylglucose) transport in cerebral microvascular endothelium (CMEC). The role of glucose metabolism and protein synthesis will be evaluated. Many of the parameters studied will be the same as those in Aim 1, thereby enabling us to compare the mechanism(s) by which hexose transport is downregulated in vivo in the diabetic rat and in vitro in CMEC grown in a glucose-enriched medium. 3). To determine the basis for upregulation of B-hydroxybutyrate transport across the BBB in diabetes and its relation to altered hexose transport. 4). To determine the functional consequences of altered transport and fuel metabolism in microvessels of diabetic rats. The ability to maintain myo-inositol and glutathione content, NaK ATPase activity and AIB transport will be assessed in microvessels from at least two sites and in isolated glomeruli. The effect of diabetes on O2 consumption and fuel metabolism in these tissues will also be examined. 5). To determine the effect of hyperglycemia on myo-inositol transport, polyol metabolism and NaK ATPase in CMEC and pericytes. These studies should provide fundamental information about the early metabolic and functional alterations produced by diabetes in the microvasculature and the mechanisms by which they occur. They will hopefully provide a groundwork for understanding the dysregulation of signal transduction in the microvasculature and for developing metabolically-based therapies to prevent the development of microvascular disease.